Many liquid or other fluent materials are conveniently transported by truck, although they may also be transported by railcar, barge or by other means. Trucks that are used to transport such materials may include a frame on which a container is mounted, or they may comprise a tractor and an attached trailer having a container mounted thereon. Gasoline and other petroleum products are often transported by a tractor and an attached trailer to which a generally-cylindrical container is mounted. The support frame for a container trailer (or for a truck on which a container is mounted) typically includes a base frame which supports the container and a suspension frame which includes the wheel/axle assembly and the suspension system. Container trailers which travel on interstate highways in the United States are required to have a circumferential supports for the container that are spaced no more than 60 inches apart along the length of the container. Since such containers are often used to haul more than one product, such as gasoline products of different grade, at the same time, they are commonly provided with internal bulkheads to separate product compartments within the container. These internal bulkheads may be located so as to provide the necessary circumferential reinforcement for the structure of the assembly.
Typically, the container is fabricated in one assembly and the base frame and suspension frame are fabricated in another assembly. In most circumstances, all three components, the container, the base frame and the suspension frame are separately fabricated and the two frame components are welded or bolted together prior to mounting of the container thereon. Conventionally, the body of the container is assembled from four components, a top component, a bottom component and two side components, to comprise a generally cylindrical enclosure. The four components, which are not usually of the same thickness, are generally comprised of sheet aluminum or similar material that is rolled or otherwise formed so that when assembled, the components comprise a generally cylindrical structure. In conventional construction for a container that is adapted to be mounted on a truck or trailer, the bottom and two side components are welded together to form a generally U-shaped structure, the bulkheads are then welded into place, and the top component is then welded to the side components and to the bulkhead. Then an end cap is welded to each end of the generally cylindrical enclosure to complete the assembly.
Because the various product compartments of a truck or trailer mounted container are unloaded at different times, conventional bulkheads are generally comprised of a flanged dish to permit them to withstand the pressures exerted on one side or the other. These flanged dish bulkheads are themselves fabricated in a process involving several steps. Generally a blank is cut from a sheet of aluminum or other metal, and a press (such as a vacuum forming press) is employed to form the blank into a dome-shaped or dish-shaped structure. Then a flange is formed around the periphery of the domed structure, which flange is adapted to adjoin the interior surface of the container. In some cases, a vacuum forming press or other press can be used to form the blank directly into a flanged dish. In most cases, however, the flanged edge must be separately formed and then trimmed. Frequently, reinforcing ribs must also be fabricated and welded to the flanged dish. The flanged dish is then welded by human welders to the adjoining interior surface of the partially formed container. When all of the flanged dish bulkheads are installed in the partially completed container, the top component of the container is welded to the two side components and to the flanged dish bulkhead.
A fabrication process requiring so many steps and components is generally not suitable for robot welding. It is common, therefore, for all of the welds in such a process to be made by human welders instead of robot welders. Consequently, the conventional process for fabricating and assembling a container is slow, labor-intensive and expensive. In addition, such a process is susceptible to errors of fit of the various components with respect to each other. Furthermore, in an attempt to correct errors in fit between the components, large welds are often made to fill in the gaps between components. Such large welds may contribute increased weight and may cause heat distortion in the finished container.
It would be desirable if a manufacturing method and design for a container having bulkheads could be devised that would reduce or minimize the number and complexity of the steps required for fabrication and assembly. It would also be desirable if such a method and design could be devised that would reduce or minimize the risk of human error in the assembly process. It would also be desirable if such a method and design could be provided that would provide for more accurate fit of the various components, thus reducing the size of the welds required and reducing the effects of heat distortion due to such welds. It would also be desirable if such a method and design could be developed that would require fewer and less complex components than conventional designs.